Allow using --session=none to override startup_session

Fixes #6131

kitty/boss.py

@@ -763,8 +763,11 @@ class Boss:
             args.args = rest
             opts = create_opts(args)
             if data['session_data']:
-                from .session import PreReadSession
+                if data['session_data'] == 'none':
-                args.session = PreReadSession(data['session_data'], data['environ'])
+                    args.session = 'none'
+                else:
+                    from .session import PreReadSession
+                    args.session = PreReadSession(data['session_data'], data['environ'])
             else:
                 args.session = ''
             if not os.path.isabs(args.directory):

kitty/cli.py

@@ -898,6 +898,8 @@ Path to a file containing the startup :italic:`session` (tabs, windows, layout,
 programs). Use - to read from STDIN. See the :file:`README` file for details and
 an example. Environment variables in the file name are expanded,
 relative paths are resolved relative to the kitty configuration directory.
+The special value :code:`none` means no session will be used, even if
+the :opt:`startup_session` option has been specified in kitty.conf.
 
 
 --hold

kitty/main.py

@@ -85,6 +85,8 @@ def talk_to_instance(args: CLIOptions) -> None:
     session_data = ''
     if args.session == '-':
         session_data = sys.stdin.read()
+    elif args.session == 'none':
+        session_data = 'none'
     elif args.session:
         with open(args.session) as f:
             session_data = f.read()

kitty/options/definition.py

@@ -2938,7 +2938,7 @@ opt('startup_session', 'none',
     option_type='config_or_absolute_path',
     long_text='''
 Path to a session file to use for all kitty instances. Can be overridden by
-using the :option:`kitty --session` command line option for individual
+using the :option:`kitty --session` :code:`=none` command line option for individual
 instances. See :ref:`sessions` in the kitty documentation for details. Note that
 relative paths are interpreted with respect to the kitty config directory.
 Environment variables in the path are expanded. Changing this option by

kitty/session.py

@@ -205,19 +205,22 @@ def create_sessions(
     default_session: Optional[str] = None,
 ) -> Iterator[Session]:
     if args and args.session:
-        environ: Optional[Mapping[str, str]] = None
+        if args.session == "none":
-        if isinstance(args.session, PreReadSession):
+            default_session = "none"
-            session_data = '' + str(args.session)
-            environ = args.session.associated_environ  # type: ignore
         else:
-            if args.session == '-':
+            environ: Optional[Mapping[str, str]] = None
-                f = sys.stdin
+            if isinstance(args.session, PreReadSession):
+                session_data = '' + str(args.session)
+                environ = args.session.associated_environ  # type: ignore
             else:
-                f = open(resolve_custom_file(args.session))
+                if args.session == '-':
-            with f:
+                    f = sys.stdin
-                session_data = f.read()
+                else:
-        yield from parse_session(session_data, opts, environ=environ)
+                    f = open(resolve_custom_file(args.session))
-        return
+                with f:
+                    session_data = f.read()
+            yield from parse_session(session_data, opts, environ=environ)
+            return
     if default_session and default_session != 'none':
         try:
             with open(default_session) as f: